This invention relates to test kits for detecting acidity in a lubricant of a climate control system which may contain a leak detection dye.
In climate control systems, such as heating, cooling, ventilating, and air conditioning systems, lubricants oils are tested for acidity as an indication of suitability for continued use and as a means for detecting contamination of the climate control system. Acid test kits for use with climate control systems can show whether or not the acidity of the lubricant is low enough to continue using the lubricant in the system. The test kit can show a useable range of acid content (acid number) in the lubricant, a range where the user should be aware that lubricant replacement may be suggested, and a range where the climate control system should not be used until the lubricant is replaced.
Colored lubricants are becoming more common due to the use of a leak detection dye, such as a naphthalimide dye, in climate control systems, which can make it more difficult to accurately determine the acid content of the lubricant. For example, some acidity tests, such as ASTM D974-64, are not easy to use in the field and may not perform well with highly colored lubricants because the color changes that are produced by in the test can be obscured by the color of the sample.
In general, the invention features a test kit for determining the acid content of a lubricant in a climate control system. The lubricant can contain a leak detection dye, such as a naphthalimide dye. The test kit contains an aqueous solution having a salt and a known amount of hydroxide and an organic solution containing an alcohol and an organic solvent having a flash point of at least 130xc2x0 F., preferably 150xc2x0 F. or higher. When a lubricant is added to a combination of the aqueous solution and the organic solution, the mixture separates into a bottom layer and an upper layer. The color of the bottom layer clearly indicates the acid content of the lubricant and reliably provides the range of acid content of the lubricant. The indicator colors are distinct from the color of the lubricant, for example, the color of the leak detection dye, and do not cause confusion with the color of the lubricant.
In one aspect, the invention features an acid test kit for determining the acidity of a lubricant from a climate control system. The kit includes an aqueous solution including water, a salt, and a hydroxide and an organic solution including a pH indicator, 2-propanol, and an organic solvent having a flash point of at least 130xc2x0 F.
In another aspect, the invention features a process of manufacturing an acid test kit for determining acidity of a lubricant from a climate control system. The method includes dissolving a salt in a known volume of water and adding a volume of a hydroxide solution having a known concentration to form an aqueous solution; and dissolving a pH indicator in a mixture of 2-propanol and an organic solvent having a flash point of at least 130xc2x0 F. The volume of hydroxide solution added to the water and salt can form an aqueous solution having a concentration of 0.001 to 0.00001 M, depending on a threshold acid content selected for detection.
In another aspect, the invention features a method for testing the acid content of a lubricant from a climate control system. The method includes obtaining a lubricant from a climate control system, combining a first amount of the lubricant with a second volume of an organic solution including a pH indicator, 2-propanol, and an organic solvent having a flash point of at least 130xc2x0 F. and a third volume of an aqueous solution including water, a salt, and a hydroxide to form a mixture, shaking the mixture, and observing a color of a bottom layer of the mixture to determine the acid content of the lubricant. The ratio (g:mL:mL) of the first amount to the second volume to the third volume can be 6.2:9.0:8.5.
The threshold acid content of the lubricant can be between 0.05 and 0.5 total acid number (TAN), preferably 0.1 or 0.2 TAN. The threshold acid content can vary for different lubricants. The color of the bottom layer indicates the TAN of the lubricant. TAN is calculated as the quantity of base, expressed in milligrams of potassium hydroxide, that is required to titrate all acidic materials in a 1 gram sample of the lubricant that have a pKa sufficient to react with the hydroxide. For example, the color of the bottom layer is a first color when the acid content of the lubricant is 0.02 TAN or less, a second color if the acid content of the lubricant is 0.02 to 0.08 TAN, or a third color if the acid content of the lubricant is 0.1 TAN or greater. The first color can be blue, the second color can be green and the third color can be yellow.
The organic solvent is an aromatic- or aliphatic-containing hydrocarbon solvent that is free of acidic groups, such as carboxyl or hydroxyl groups, or basic groups, such as amino groups. In order to reduce the flammability of the organic solution, the organic solvent has a relatively high flash point of at least 130xc2x0 F., preferably at least 150xc2x0 F. Flash point is the temperature at which a liquid gives off a vapor sufficient to form an ignitable mixture with air near the surface of the liquid. By including an organic solvent having a relatively high flash point, the acid test kit can be less hazardous to use in the field. The organic solvent is essentially chemically inert. The organic solvent can be, for example, CHEVRON ion exchange solvent (available from Standard Oil of California) having a flash point of 195xc2x0 F., ESCAID 100(trademark) and ESCAID 110(trademark) (available from Exxon-Europe, essentially a petroleum distillate) having a flash point of 180xc2x0 F., NORPAR(copyright) 12 (available from Exxon-USA, essentially a petroleum distillate) with a flash point of 160xc2x0 F., CONOCO C1214 (available from Conoco) with a flash point of 160xc2x0 F., AROMATIC 150(trademark) (an aromatic kerosene available from Exxon-USA) having a flash point of 150xc2x0 F., and AROMATIC 200(trademark) (an aromatic kerosene available from Exxon-USA) having a flash point of 217xc2x0 F., and other commercially available kerosene and petroleum fractions. More particularly, AROMATIC 150(trademark) is a high purity aromatic mixture of about 8% C9 aromatic compounds, about 74% C10 aromatic compounds, about 15% C11 aromatic compounds, and about 1% C12 aromatic compounds, and about 1% of nonaromatic compounds. Preferably, the organic solvent can be AROMATIC 150(trademark) or AROMATIC 2000(trademark).
The test kit is a two-phase type wherein the phases separate rapidly. The separation can occur within 10 minutes, preferably within 5 minutes, more preferably within 3 minutes, and most preferably within one minute. The high ionic strength of the aqueous solution facilitates rapid separation without emulsification.
The aqueous solution can be free of alcohol. The organic solution can be free of ethanol. When the aqueous solution and organic solution are both free of ethanol, the color of the indicator is more brilliant that when the solutions include ethanol.
Additional features and advantages of the invention will become apparent from the detailed description of the invention.